Food and beverage dispensers and vending machines are used widely to store and dispense food and beverages. Typically, the food or drink product contained within such a machine must be kept below a certain temperature, either to prolong the “life” of the product and to ensure that it remains fresh, or because the consumer expects the product (for example, a drink or an ice cream) to be below a certain temperature.
In this document, such devices are referred to as “coolers”. There are several different types of cooler. A beverage dispenser/cooler typically comprises a bath of cooled fluid which houses ‘product coils’—a series of pipes through which the beverages or ingredients of beverages pass. Cooled fluid is drawn from the bath into a “python”, which includes at least one pipe containing cooled fluid from the bath and at least one pipe through which the beverage is dispensed. The proximity of both the bath to the product coil and the pipe containing cooled fluid to the dispensing pipe cools the beverage in the dispensing pipe. The fluid in the cooled fluid pipe circulates between the pipe and the bath, and so is replenished with cooled fluid from the bath.
A similar type of beverage dispenser is a carbonated cooler. In the cooler described above, chilled fluid is pumped directly from the cooler bath and circulates in the python. In a carbonated cooler, carbonated water is circulated in the python. The carbonated water is produced separately in a carbonator bowl by mixing food grade CO2 under pressure with drinking water. In order to cool this carbonated water down it is then passed through a ‘product coil’, which is situated within the cooler bath. The carbonated water can be diverted from the python into a mixing head where it is mixed directly with a flavoured syrup to produce a carbonated drink. The flavoured syrup will typically have passed through its own product coil within the cooler bath and through the python to lower its temperature prior to mixing it with the carbonated water in the mixing/dispense head. With every drink that is dispensed, the combined volume of carbonated water in the python and carbonator bowl is reduced. There are additional electronics involved in topping up the supply by measuring the level of carbonated water present in the carbonator bowl. Once it reaches a critical minimum level a carbonation cycle is instigated which re-fills it up to the maximum level again.
Another type of cooler is a “glass door” vending machine. This is a vending machine having a cooled compartment in which chilled products are stored. The compartment is accessible using a glass door. Another type of cooler is an “enclosed” vending machine, in which the cooled compartment containing products is not accessible by a customer. When a customer requires a product from the enclosed vending machine, the product is dispensed through a hatch. A further type of cooler is an “open-reach” cabinet, in which a cabinet containing chilled products is provided. The chilled products are directly accessible by a customer and a curtain of air is maintained across the access to the open reach cabinet in order to provide a degree of insulation from the ambient temperature. A further type of cooler is a “dump bin”, which comprises a cooled cabinet having an opening at the top through which a customer can access chilled products. A dump bin is not provided with a door, but may have a curtain of air to assist in maintaining a lower temperature than the ambient temperature.
The types of coolers described in the above paragraphs typically use a vapour compression cycle to maintain a low temperature. A refrigerant enters a compressor as a vapour, and is compressed. The compressed vapour passes through a condenser to cool and condense the vapour into liquid form. The liquid then passes through a restriction which causes it to evaporate and cool down. The evaporation takes place in a series of tubes or coils in an evaporation unit, which are cooled. In a beverage/dispense cooler the evaporation unit is immersed in a fluid bath. In the other types of cooler, a fan blows air over the evaporation unit. The air is cooled and circulated into the cooled cabinet and so reduces the temperature of any product stored in the cabinet.
Another type of cooler is a flat plate cooler in which ice is made and placed on a heat exchanger such as an aluminium plate. The reduced temperature of the heat exchanger is then used to cool a product.
Each of these cooling methods can be thought of as having a primary and a secondary cooling mechanism. In the case of the beverage dispenser/cooler, the primary cooling mechanism is that used to cool the bath of fluid and the secondary cooling mechanism comprises using the cooled fluid to cool a beverage. In the case of the refrigerated cabinets, the primary cooling mechanism is the compressor, condenser and evaporator which are used to cool a refrigerant, and the secondary cooling mechanism is the air which is cooled by the refrigerant and subsequently used to cool products within the cabinet.
Considering the situation where a cooler is used in a commercial environment, for example a bar or a restaurant: This environment may require that the products cooled by the cooler are sufficiently cool during trading hours, but it is not so critical to keep them cool during non-trading hours. In order to improve energy efficiency and save energy costs, it would be desirable to introduce systems that allow the cooler to maintain a required temperature during trading hours and to maintain a second required temperature during non-trading hours. The second required temperature in the case of a cooler may be higher than the required temperature during trading hours, as it is only necessary to keep the product fresh rather than provide the product at a temperature required by a customer. There are many examples of improvements to the efficiency of coolers, such as U.S. Pat. No. 4,417,450. This patent describes an energy management system that controls the cycling of a refrigeration system on the basis of trading hours.
As there are many coolers already in use, it would be desirable to allow such an energy management system to be retrofitted to existing coolers. It is possible to retrofit such systems, although this requires either a skilled engineer to visit the site where a cooler is located, or for the cooler to be sent to a site for a retrofit. This is required because the devices typically need re-wiring to connect temperature sensors to controllers, and is a time consuming and expensive process. It would be desirable for a retrofit energy management system to be fitted in such a way as to minimize the time required to retrofit the system.